Outstanding book, and attached resource list for designing and building electronics projects. Great for startups etc.
Prerequisites are basic electronics skills, such as knowing how basic components (R, C etc) work, proficiency in PCB CAD software. I think you'll get more out of it if you already have a WIP (or prior) product designed, since the advice will make more sense with context.
From the intro: > This book assumes at least a basic understanding of electrical engineering. It’s oriented towards product design and implementation, but is equally applicable to hobbyist projects, art installations, and other amateur electrical engineering projects. If you’re designing your first PCB, reading this book may help you avoid mistakes you didn’t know you were making. If you’re designing your 1000th PCB, this book will act more as a checklist to help illuminate any area you forgot to think about.